Along with the generalization of an HID (High Intensity Discharge) lamp for motor vehicles, there is an increasing demand for the reduction of a size and a weight of a head lamp unit for the HID lamp. This holds true in case of an LED head lamp unit for motor vehicles.
The head lamp unit includes a head lamp portion and a power supply device. The head lamp portion is a lighting device for emitting light. The head lamp portion includes a socket to which a HID lamp is attached and an ignitor connected to the socket. The power supply device includes a battery power supply and a voltage converter for converting a voltage of the electric power supplied from the battery power supply and outputting the electric power to the ignitor. The voltage converter includes an input connector to which an input cable for supplying the electric power from the battery power supply is connected and an output connector to which an output cable for outputting the electric power to the ignitor is connected. In recent years, with a view to reduce the size of a head lamp unit and to save costs, there is known a power converter that makes use of a one-piece-type connector in which two input and output connectors are one-piece formed with each other (see, e.g., Japanese Patent Application Publication No. 2003-132979). There is also known a power converter in which a mounting substrate of a power converter circuit having input and output connectors is fixed to an accommodation case by screws (see, e.g., Japanese Patent No. 4479369)
The aforementioned power converter circuit is typically formed of an inverter, a chopper circuit and so forth. It is known that, depending on a loop antenna model or the like, the power converter circuit tends to generate a radiation noise affecting an output voltage. In order to reduce the size of the power converter, however, it is required to remove an unnecessary noise or to suppress the influence of the radiation noise at a significantly high level. In the event that an input connector and an output connector are one-piece formed with each other, the electric power inputted to the input connector is highly susceptible to a noise contained in the electric power outputted from the output connector. This is one of the causes hindering the size reduction of the power converter employing a one-piece-type connector.